Thermal cut-out or fuse for electric circuits.



No. 738,908. PATENTED SEPT. l5, 1903. v

R. EUNDHAUSBN.

THERMAL CUT-CUT 0R FUSE POR ELECTRIC CIRCUITS.

JAPPLICATION FILED DBO. 15, 1899. RENEWBD 11,111.1, 1901.

No MODEL.

ne. frescos'.

Usuari-3D` STATES Patented September 15, 1903.

PATEnln OFFICE.;

RUDOLF I-IUNDHASEN, OF WILMERSDORF, NEAR BERLIN, GERMANY, AS- SIGNOR TO THE SIEMENS t HALSKE ELECTRIC COMPANY OF AMERICA, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

THERMAL CUT-OUT'OR FUSE FOR ELECTRIC CIRCUITS.

SPECIFICATION lforming' part of Letters Patent No. 738,908, dated September 15, 1903. Application led December l5, 1899. Renewed March l, 1901. Serial No. 49,475. (No model.)

My invention has for its object the provision of an improved safety-fuse of the class.

described by the use of which the danger and the force of the explosion ou the occurrence of a short circuit is materially decreased.

It has been customary in employing electric fuses, especially in connection with highpotential circuits, to inclose the terminal portions of the fuse-wires in cement, gypsum, or some other self-hardening insulating mate- 2 5 rial, leaving the remainder of the wire exposed. Upon a rupture of a fuse due to an overload or short circuit explosions frequently occur, which scatter fine metallic particles and result in flames which tend to maintain 3o a short circuit between the terminals of the ruptured `fuse and which may shortcircuit neighboring conductors.

In accordance with my invention I so construct fuse-plugs having concentric terminals that I decrease the harmful effects caused upon a rupture of the fuse by surrounding the immediate portion of the fuse-Wire with talc or talcum powder, which I have found to be a substance that contains to a high degree 4o the power of readily absorbing the gases and metallic vapors resulting upon melting the fuses. Ihave heretofore devised an improved fuse employing talcum powder -for the purpose` of absorbing metallic particles that would otherwise be scattered upon the blowing of the fuse, and my invention herein relates more particularly to a new construction of a fuse in which talcum powder or some similar material possessing its characteristics 5o is employed. There are additional features of my invention which will be more fully set forth hereinafter.

I will more particularly explain my invention by reference to the accompanying drawings, in which- Figure lis a vertical section through the center of a fuse-plug constructed in accordance with the'invention, one terminal of the fuse being shown in complete elevation. Fig. 2 is a top view of the plug shown in Fig. l, theA cover being removed.

Like parts are indicated by similar letters o f reference throughout both gures.

The plug-fuse shown comprises a hollow cylindrical base or shell c, having its lower end reduced and provided with an exterior metallic terminal I, threaded thereon, and a center metallic terminal m, located in a recess formed `in the end thereof, and extending through the plug are a main-fuse wire g and a supplementary or indicator fuse wire 7s. Oneend of the fuse g is soldered to the terminal I, while the other end is soldered to a threaded extension of the central terminal m. The threaded extension of the terminal m passes through an axial bore in the bottom wall cl of the shell c, a threaded washer or nut fn, engaging the threaded stem of the terminal m to secure the latter in place. Each fuse g and lc is preferably looped, two division-walls o and/p being interposed, respectively, between the sides of the looped fuse g and the looped fuse lc. The terminal parts of the "fuses are preferably embedded in gypsum or any suitable cement, while the middle por- 85 tions of the fuses are embedded in talcum powder or other suitable material capable of absorbing the metallic vapor arising when the fuses are blown. f

The partition-Walls 0 and p as constructed serve, further, to reinforce the talcum v'powder to prevent' metallic vapor from passing from one end of each fuse to the other. In the construction shown the centralspace between the partitions o and p isv filled with talcum powder, which prevents metallic vapors from the fuse k, which is the last to .be blown, from mingling with the metallic vapor due to the fuse g. The wall of the casing c of the fuse-plug is preferably of reduced roo strength and thickness at one or more places, as indicated at q, so that the shell c will not be ruptured except at the'weakened places upon explosions occurring when the fuses are blown.

The fuse 7c is in the nature of a supplemental fuse and is preferably so constructed that it cannot possibly burn before or at the same time with the main fuse, it being desirable to have it burn after the main fuse is blown The desired result is accomplished by so constructing the supplemental fuse that an abnormal iow of current in the protected circuit that would cause a rupture of the main fuse when divided between the same and the supplemental fuse would not cause a rupture of the supplemental .fuse if the path closed by the main fuse were left intact, or, in other words, the same proportion of this abnormal current initially flowing through the supplemental fuse would not in itself be sufficient;`

to burn the same, so that the supplemental fuse cannot possibly burn until the main fuse is blown. The purpose of the supplemental fuseis to serve as anindicating meanswhercby the working condition of the main fuse may be determined, and in order to permit the supplemental fuse to be seen I preferably locate the same before an opening r in the wall of the fuse-casing, a small portion of the gypsum or cement being removed from the space between the su pplementaifuse and the opening.

It is evident that a number of different applications may be made of the invention herein shown and particularly described without departing from the spirit thereof, and I do not, therefore, wish to be limited to the precise construction shown.

Having thus described my invention, I claim as new and desire to secure by Letters Patentl. In a fuse-plug, the combination with an inclosing shell, of an annular circuit-terminal carried thereby, a second terminal arranged substantially concentric with the aforesaid terminal, a fuse-wire uniting the terminals, and talc or othersuitable powdered material within the casing and surrounding the fuse-wire, the insulating-shell being provided with a portion of reduced strength, whereby upon an explosion this portion will be the Iirst to be ruptured, substantially as described.

2. In a fuse-plug, the combination with a hollow cylindrical shell, composed of insulating material, of an annular terminal carried thereby, a second terminal substantially concentric with the annular terminal, also carried thereby, a main fuse uniting the said terminals, a supplemental fuse of less capacity, also uniting the said terminals, the wall of the casing being constructed to permit of the observation of the supplemental fuse, and talc or other suitable powdered material within the hollow of the shell surrounding the fuse-wires, substantially as described.

8. In a fuse-plug, the combination with a hollow cylindrical shell, of two terminals carried thereby, a main and a supplemental fuse wire uniting the said terminals, the said fuse-Wires being bent in the form of loops, a partition-wall interposed between the sides of each loop, and talc or other suitable powdered material within the hollow ofthe cylindrical shell surrounding` the fuse-Wires, substantially as described.

4. In a thermal cut-out, the combination with an inclosing hollow shell provided with an opening, of a main fuse and a supplementary fuse within the shell, the latter fuse being visible from the exterior through the opening, a projection in the interior adjacent the supplementary fuse, a suitable material for blocking the passage from the hole in the shell to the interior between the shell and the projection. 5. In a device of the class specified, the combination of a cylindrical casing having an inner wall arranged near one of its sides and also having an aperture in its outer Wall opening into the passage between said inner Wall and outer wall, a central terminal extending into the interior of the casing, and an annular terminal surrounding the exterior of the same, a loop-fuse extending between terminals and having its legs arranged on oppo site sides of the said wall of the casing, and a body of talc or other suitable powdered material within the casing and associated with the fuse, substantially as described.

6. In a device of the class specified, the combination of a shell or casing having an inner wall arranged near its outer wall, an interior central terminal and an exterior annular terminal, a loop-fuse extending between terminals and having one of its legs ex'- tending into the passage between said walls, and cement arranged within said passage the shell or casing having an aperture affording an opening tothe space between it and the interior wall, and the cement being arranged to permit the fuse to be seen through said opening, substantially as described.

7. In a device of the class specified, the combination of a shell or casing having interior walls arranged near its sides and having an aperture in its outer wall opening into the passage between the saine and the adjacent inner wall, an interior central terminal and an exterior terminal surrounding the casing, main andsupplemental fuses extended between terminals, the said fuses being looped and arranged so that one leg of each fuse extends through the passage between one of the inner walls and the outer wall and the supplemental fuse being arranged in the passage into which the said aperture opens, cement within said passage, and absorbing material within the casing and associated with the fuses, substantially as described.

8. In a fuse-plug, the combination of` an insulating base or shell provided with a portion of reduced strength, metallic terminals ICO IIO

supported by said base or shell, and a fusebase or shell whereby observation of the sup- 1o Wire extending through said base or shell and plemental fuse is permitted. attached at its ends to said contacts. In witness whereof I hereunto subscribe my 9. In a fuse-plug, the combination of an inn ame this 24th day of Marchg A. D. 1899.

vsuiztting base-or shell of insulating material, RUDOLF HUNDHAUSEN a center terminal and a. concentric annular terminal secured to said base or shell, main Wtnessem' and supplemental fuses connecting said ter- WOLDEMAR HAUPT, minals, and provisions in the Wall of said HENRY HASPER. 

